Minor grammar fixes for the vintage AddASetting.md doc (#16188)

## Summary of the Pull Request
Added some Punctuation Marks as Required.
## References and Relevant Issues
None.
## Detailed Description of the Pull Request / Additional comments
There were some missing Punctuation Marks(Ex: Colon(:) and Full
Stop(.)), so I have added them.
## Validation Steps Performed

doc/AddASetting.md

@@ -5,10 +5,10 @@
       `.../console/published/wincon.w` in the OS repo when you submit the PR.
       The branch won't build without it.
     * For now, you can update winconp.h with your consumable changes.
-    * Define registry name (ex `CONSOLE_REGISTRY_CURSORCOLOR`)
-    * Add the setting to `CONSOLE_STATE_INFO`
+    * Define registry name (ex: `CONSOLE_REGISTRY_CURSORCOLOR`)
+    * Add the setting to `CONSOLE_STATE_INFO`.
     * Define the property key ID and the property key itself.
-        - Yes, the large majority of the `DEFINE_PROPERTYKEY` defs are the same, it's only the last byte of the guid that changes
+        - Yes, the large majority of the `DEFINE_PROPERTYKEY` defs are the same, it's only the last byte of the guid that changes.
 
 2. Add matching fields to Settings.hpp
     - Add getters, setters, the whole drill.
@@ -17,9 +17,9 @@
     - We need to add it to *reading and writing* the registry from the propsheet, and *reading* the link from the propsheet. Yes, that's weird, but the propsheet is smart enough to re-use ShortcutSerialization::s_SetLinkValues, but not smart enough to do the same with RegistrySerialization.
     - `src/propsheet/registry.cpp`
         -  `propsheet/registry.cpp@InitRegistryValues` should initialize the default value for the property.
-        -  `propsheet/registry.cpp@GetRegistryValues` should make sure to read the property from the registry
+        -  `propsheet/registry.cpp@GetRegistryValues` should make sure to read the property from the registry.
 
-4. Add the field to the propslib registry map
+4. Add the field to the propslib registry map.
 
 5. Add the value to `ShortcutSerialization.cpp`
     - Read the value in `ShortcutSerialization::s_PopulateV2Properties`
@@ -30,11 +30,11 @@ Now, your new setting should be stored just like all the other properties.
 
 7. Update the feature test properties to get add the setting as well
     - `ft_uia/Common/NativeMethods.cs@WinConP`:
-        - `Wtypes.PROPERTYKEY PKEY_Console_`
-        - `NT_CONSOLE_PROPS`
+        - `Wtypes.PROPERTYKEY PKEY_Console_`.
+        - `NT_CONSOLE_PROPS`.
 
 8. Add the default value for the setting to `win32k-settings.man`
     - If the setting shouldn't default to 0 or `nullptr`, then you'll need to set the default value of the setting in `win32k-settings.man`.
 
-9. Update `Settings::InitFromStateInfo` and `Settings::CreateConsoleStateInfo` to get/set the value in a CONSOLE_STATE_INFO appropriately
+9. Update `Settings::InitFromStateInfo` and `Settings::CreateConsoleStateInfo` to get/set the value in a CONSOLE_STATE_INFO appropriately.